Sun Protection Factors (SPF): What they mean
Every bottle or tube of sunscreen has an SPF number on it, but what do these numbers mean?
“In Australia, the Cancer Council recommends using sunscreen that's SPF30 or higher, because we’ve got such a high ultraviolet – or UV – environment,” Walker says.
“The SPF refers to the time it takes your skin to get damaged. So if it's an SPF30, in theory it takes 30 times as long for damage to happen than it would without the sunscreen on.”
The numbers seem large, but the difference between SPF30 and SPF50 is minimal, says Walker. A factor of 50 would let 2 per cent of UV rays through, while a factor of 30 would let 3.3 per cent through.
How the sun damages our skin
Nearly all skin cancers are caused by too much UV radiation from the sun, which permanently damages skin cells. Two in three Australians will develop some form of skin cancer before the age of 70.
According to the Cancer Council, even mild sunburn can increase your risk of developing melanoma, and the more often you get burnt and the worse the burn, the higher your risk.
The first 10 years of childhood is an especially vulnerable time because children’s skin is more sensitive, says Walker.
Find a sunscreen you love and use it regularly
You’ll be more likely to use sunscreen if you find one you like, says Walker. “Otherwise, you're not going to be comfortable wearing it and then you're less likely to use it.”
Choose a sunscreen that:
- Has a SPF of 30 or higher
- Is broad spectrum, so it protects against both UVA and UVB radiation
- Is water resistant
Don’t skimp on sunscreen
How effective sunscreen is depends on how well it’s applied. Most of us aren’t using enough: in fact, 85 per cent of Australians don’t apply enough sunscreen, says Walker.
“Sunscreen is only as good as the person applying it,” she says.
Adults should use seven teaspoons for a full-body application: one for each arm, each leg, front of your body, back of your body, and then one for your face neck and ears.
“And remember to reapply every two hours, or more often if you’ve been swimming or sweating a lot,” says Walker.
Don’t forget to slip, slop, slap, seek and slide
Sunscreen is easy and convenient to use, but don’t rely on it alone, says Walker.
Remember sunscreen is a screen, not a block. “Don’t use it to extend your time in the sun. It's not a suit of armour.”
For the best sun protection, use sunscreen with a combination of other sun protection measures: clothing, hats, sunglasses and shade.
“Using those five in combination will give you the best protection,” Walker says.
Should you wear sunscreen every day?
The answer depends on where you are, the time of year and how long you’ll be outdoors.
For instance, if you’re in northern Australia where the UV level is always 3 or above, you’ll need to wear sunscreen when you’re outdoors all year round, even in winter.
If you’re in southern Australia, you’ll need to wear sunscreen every day the UV is forecast to be 3 or above, usually between mid-August and April. You can find out the UV levels for your local area with the SunSmart app or through the Bureau of Meteorology .
Of course, it also depends on how long you’ll be outside. If you work outdoors all day, you can get burnt even if the UV level is low, Walker says.
It’s easy to get sunburnt accidentally
More of us are getting sunburnt by accident if we spend more time in the sun than we expect, such as waiting at a bus stop, says Walker.
Even on cool, cloudy days, UV radiation can be high – but you won’t feel it. And by the time your skin starts to burn, it’s already been damaged.
“Putting sunscreen on in the morning means that you'll then have a level of protection against incidental sun exposure even if you get caught out. It's a good routine to get into,” says Walker.
It’s never too late to protect your skin
If you’ve been sunburnt as a child (and most Australians have) you can still reduce your risk of skin cancer by protecting your skin now and in the future.
Even for people who grew up covering themselves in oil and sunbaking on the beach, prevention is still important, says Walker.
“People often think that the damage has been done, but it’s never too late to reduce your risk. The more you use sun protection at any stage of life, the more chance you have of reducing your risk of skin cancer.”
Heather Walker is Chair of Cancer Council’s National Skin Cancer Committee.
